Hi Dietrich,
How do I select the default for the poll?
How do I select other types of poll questions as multiple choice, sliding bar, number input, etc.?
Unfortunately, these are not possible currently.
How do I prevent users from voting twice in a poll?
If you are referring to users changing their response, then unfortunately there is no setting to prevent this.
If you are referring to preventing multiple responses, this can be done at the polls setting section(
http://take.ms/DGDyy).
How do I include multiple questions in the poll?
Each question/reply can only associate with one poll. This means that you have to create multiple replies with their respective polls if you want to have multiple polls in one discussion.